Elsevier

Journal of Power Sources

Volume 184, Issue 2, 1 October 2008, Pages 578-582
Journal of Power Sources

Short communication
Synthesis and performance of lithium vanadium phosphate as cathode materials for lithium ion batteries by a sol–gel method

https://doi.org/10.1016/j.jpowsour.2008.01.007Get rights and content

Abstract

Monoclinic lithium vanadium phosphate, Li3V2(PO4)3, was synthesized by a sol–gel method under Ar/H2 (8% H2) atmosphere. The influence of sintering temperatures on the synthesis of Li3V2(PO4)3 has been investigated using X-ray diffraction (XRD), SEM and electrochemical methods. XRD patterns show that the Li3V2(PO4)3 crystallinity with monoclinic structure increases with the sintering temperature from 700 to 800 °C and then decreases from 800 to 900 °C. SEM results indicate that the particle size of as-prepared samples increases with the sintering temperature increase and there is minor carbon particles on the surface of the sample particles, which are very useful to enhance the conductivity of Li3V2(PO4)3. Charge–discharge tests show the 800 °C-sample exhibits the highest initial discharge capacity of 131.2 mAh g−1 at 10 mA g−1 in the voltage range of 3.0–4.2 V with good capacity retention. CV experiment exhibits that there are three anodic peaks at 3.61, 3.70 and 4.11 V on lithium extraction as well as three cathodic peaks at 3.53, 3.61 and 4.00 V on lithium reinsertion at 0.02 mV s−1 between 3.0 and 4.3 V. It is suggested that the optimal sintering temperature is 800 °C in order to obtain pure monoclinic Li3V2(PO4)3 with good electrochemical performance by the sol–gel method, and the monoclinic Li3V2(PO4)3 can be used as candidate cathode materials for lithium ion batteries.

Introduction

In an intensive search for alternative materials, transition metal oxides have been the focus of a wide developing effort as cathode materials [1], [2], [3], [4]. Recently, lithium conducting phosphates, Li3M2(PO4)3, and materials based on these compounds have emerged as the most promising candidates [5], [6], [7], [8]. Of these materials, monoclinic Li3V2(PO4)3 [9], unlike the rhombohedral one [10], exhibits a complex series of two-phase transitions on Li extraction, followed by a solid solution regime on lithium reinsertion. The reversible cycling of all three lithium from Li3V2(PO4)3 would correspond to a theoretical capacity of 197 mAh g−1 [11], [12], [13], [14], which is the highest for all phosphates reported. Usually, synthesis of Li3V2(PO4)3 is mainly performed via hydrogen reduction method [15], which needs high reaction conditions. It is difficult to obtain Li3V2(PO4)3 sample with small particle and homogeneous distribution, which is critical to its electrochemical performance. Compared with solid state reaction method, sol–gel method can mix the starting ingredients at molecular level. It has enormous advantages such as lower calcination temperature, shorter sintering time and smaller particle size for the resultant powder [16], [17]. Thus, sol–gel method is a novel concept for the synthesis of an improved Li3V2(PO4)3.

In this context, monoclinic Li3V2(PO4)3 was synthesized by a sol–gel method. Residual carbon left over from the sol–gel method is useful for its electrochemical improvement. It is investigated for the influence of sintering temperatures on the structure, the morphology and the electrochemical properties of monoclinic Li3V2(PO4)3.

Section snippets

Experimental

The samples were prepared by the sol–gel method using LiOH·H2O, NH4VO3, H3PO4 and citric acid as raw materials in the molar ratio of 3.05:2.00:3.00:2.00. Citric acid was dissolved in optimal distilled water, and then added aqueous solution of NH4VO3 and LiOH·H2O in sequence under continuously stirring. The obtained sol darkened after adding H3PO4. In order to make metal ions chelated by citric acid thoroughly, adjust the sol PH to about 9 using NH3·H2O until the solution color gradually turned

Results and discussion

In order to determine preheating and calcining temperature of the dry gel mixture, TG and DTA were performed. TG/DTA spectra for the gel precursor obtained are shown in Fig. 1.

The thermogram (TG) shows that weigh loss took place in several main steps. The first step occurred between room temperature and 120 °C with ∼4% weight loss, which was mainly attributed to the removal of water from the gel. The following step of around 40% weight loss between 120 and 500 °C was the decomposition of lithium

Conclusions

Monoclinic Li3V2(PO4)3 has been successfully synthesized by a sol–gel method under Ar/H2 (8% H2) atmosphere. The influence of sintering temperatures between 700 and 900 °C on the synthesis of Li3V2(PO4)3 has been investigated. Charge–discharge tests show that the 800 °C-sample exhibits the highest initial discharge capacity of 131.2 mAh g−1 and good capacity retention between 3.0 and 4.2 V at the current density of 10 mA g−1. It is suggested that the optimal sintering temperature is 800 °C in order to

Acknowledgements

This research was sponsored by the Natural Science Foundation of Hubei Province (No. 2006ABA317). The author would like to thank Prof. H.X. Liu for his guide at State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, and thanks Dr. M.H. Cao for his help.

References (19)

  • S. Megahed et al.

    J. Power Sources

    (1994)
  • C. Yang et al.

    Solid State Ionics

    (2006)
  • K.S. Nanjundaswamy et al.

    Solid State Ionics

    (1996)
  • D. Morgan et al.

    J. Power Sources

    (2003)
  • Y. Hu et al.

    Mater. Chem. Phys.

    (2005)
  • L.J. Fu et al.

    Prog. Mater. Sci.

    (2005)
  • P. Fu et al.

    J. Power Sources

    (2006)
  • X. Zhu et al.

    Solid State Ionics

    (2008)
  • M.S. Whittingham

    Chem. Rev.

    (2004)
There are more references available in the full text version of this article.

Cited by (68)

  • Heat and mass transfer characteristics during spray drying of Na<inf>2</inf>Fe<inf>0.6</inf>Mn<inf>0.4</inf>PO<inf>4</inf>F/C cathode material for Na-ion batteries

    2023, Applied Thermal Engineering
    Citation Excerpt :

    The production process of the electrode materials controls the shape, size, and structure of the electrode particles produced through the process. Several methods are used to produce the electrode materials, including the notable synthesis methods, solid-state synthesis[12,13], co-precipitation methods [14–17], sol–gel methods [18–20], the spray methods that comprise the spray pyrolysis [21–24] and spray drying [25–27], and solution combustion methods[28]. Among the various synthesis methods for the electrode materials, the spray-based approaches, spray pyrolysis, and spray drying are rapid[29], scalable[30,31], and able to produce spherical particles[32] due to the surface tension of the droplets atomized with the nozzle used in these processes.

  • Sol-gel synthesis and electrical characterization of doped-carbon decorated mixed conductor ceramics

    2019, Materials Science and Engineering: B
    Citation Excerpt :

    Consequently, their cycling performance is improved. Since, Li-ion batteries require cathode active materials having large energy density, high output power and the best possible safety performance, monoclinic Li3V2(PO4)3 (LVP) has been extensively studied as a promising cathode material [6–24]. In the LVP material structure it is possible to identified three different mobile Li+ ions.

View all citing articles on Scopus
View full text